1. Field of the Invention
The present invention relates generally to magnetic tape cassettes and, more particularly, to a magnetic tape cassette having a braking member which locks a reel hub so that the reel hub can be inhibited from being rotated uselessly when the magnetic tape cassette is not in use.
2. Description of the Prior Art
Conventionally, in a magnetic tape cassette for accommodating therein a magnetic tape on which a signal such as a video signal, a PCM (pulse code modulated) signal or the like is recorded at high density, various magnetic tape cassettes are now available on the market. Each of these magnetic tape cassettes incorporates therein a braking member to lock the reel hub so that the reel hub is inhibited from being rotated uselessly in order to prevent the magnetic tape from slackening when the magnetic tape cassette is not in use. These conventional magnetic tape cassettes might be, for example, a 1/2-inch video tape cassette, an 8 mm video tape cassette or the like.
More specifically, when this magnetic tape cassette is not in use, this braking member is biased by the spring-biasing force of a spring in a direction so that it is urged against the reel hub, thereby locking the reel hub so that the reel hub cannot be rotated. When the magnetic tape cassette is in use, the braking member is moved to the direction in which it is isolated from the reel hub by a lock releasing pin inserted thereto from the outside of the cassette casing. Thus, the locking of the reel hub is released.
The magnetic tape cassette having such braking member is of the type of a so-called one side use so that only one side of the magnetic tape can be recorded and reproduced, that is, the tape cassette cannot be turned over in use. For this reason, the braking member is adapted to perform the lock releasing operation only from one of the upper and lower parts of the cassette casing. For example, when the magnetic tape cassette is loaded onto a cassette tape recorder, the lock releasing pin is inserted into the magnetic tape cassette from its lower part side and the hub lock releasing operation of the braking member is performed by this lock releasing pin.
However, in a magnetic tape cassette in which a PCM signal is recorded on a magnetic tape at high recording density, a novel tape cassette of a double-sided use type has been developed recently, in which the two sides of the magnetic tape can be recorded and reproduced. In that case, since the cassette casing is turned over to use the two sides of the magnetic tape, the hub lock releasing operation of the braking member cannot be performed by the conventional braking member which performs the hub lock releasing operation only from the one side of the cassette casing.
Therefore, a magnetic tape cassette is required in which the braking member can be operated from two sides of the cassette casing. All of the existing magnetic tape cassettes are of the above-mentioned type so that the braking member can be operated only from the one side of the cassette casing. Thus, a magnetic tape cassette in which the hub lock releasing operation can be performed from the two sides of the cassette casing is not yet proposed.